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Title: The Chinese Performance-based Code for Fire-resistance of SteelStructures
Authors: Chao Zhang, Tongji UniversityChao Zhang, Tongji University
Subject: Fire & Safety
Keywords: Code ComplianceFire SafetySteel
Publication Date: 2013
Original Publication: International Journal of High-Rise Buildings Volume 2 Number 2
Paper Type: 1. Book chapter/Part chapter2. Journal paper3. Conference proceeding4. Unpublished conference paper5. Magazine article6. Unpublished
© Council on Tall Buildings and Urban Habitat / Chao Zhang; Chao Zhang
ctbuh.org/papers
International Journal of High-Rise Buildings
June 2013, Vol 2, No 2, 123-130International Journal of
High-Rise Buildingswww.ctbuh-korea.org/ijhrb/index.php
The Chinese Performance-based Code for
Fire-resistance of Steel Structures
Guo-Qiang Li1† and Chao Zhang2
1State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, 1239 Siping Road, Shanghai, China2College of Civil Engineering, Tongji University, 1239 Siping Road, Shanghai, China
Abstract
In the past two decades, researchers from different countries have conducted series of experimental and theoretical studiesto investigate the behaviour of structures in fire. Many new insights, data and calculation methods have been reported, whichform the basis for modern interdisciplinary structural fire engineering. Some of those methods are now adopted in quantitativeperformance-based codes and have been migrated into practice. Mainly based on the achievements in structural fire researchat China, the Chinese national code for fire safety of steel structures in buildings has been drafted and approved, and will bereleased in this year. The code is developed to prevent steel structures subjected to fire from collapsing, ensure safe evacuationof building occupants, and reduce the cost for repairing the damages of the structure caused by fire. This paper presents themain contents of the code, which includes the fire duration requirements of structural components, fundamental requirementson fire safety design of steel components, temperature increasing of atmosphere and structural components in fire, loading effectand capacity of various components in fire, and procedure for fire-resistant check and design of steel components. Theanalytical approaches employed in the code and their validation works are also presented.
Keywords: Fire-resistance, Steel structures, Code, Safety evaluation, Design
1. Introduction
Fire is a disastrous effect on steel structure since the
strength of steel will be greatly reduced with temperature
increasing. For the design of steel structures for buildings
where fire is likely to happen, fire-resistance has to be
considered. The requirements of fire-resistance for steel
structures are usually expressed as the fire-resistant dura-
tion for various structural components. To satisfy the re-
quirements, the experiments on fire-resistance of steel
components with or without fire protection can be con-
ducted. However, there are a number of disadvantages to
use experimental approach for fire safety design of steel
components. Firstly, it is hard to consider the effects of
the various load ratios over the component capacity in
reality on the fire-resistance of the component through one
or a few experiments. Secondly, it is difficult to simulate
the restraint of adjacent structure relative to the consi-
dered component in the experiment, which has usually
important effects on the fire-resistance of the component.
Thirdly, the thermal effect is hard to be considered in the
experiment. And finally, the cost of experiments is high.
Hence, the advanced approach for fire-resistant design of
steel components is based on fire safety check through
analysis, which has been employed by BS5950 (1990),
EC3 (2002), AS4100 (1990), etc.
The research on behaviour of steel structures subject to
fire started from 1990 in China (Li et al., 1999). Since
then lots of achievements have been made through theo-
retical and experimental research. Based on the achie-
vements (Li et al., 1996, 1999; H. S. Zhou, 2004; H. Y.
Zhou, 2004), the first code in China on fire safety of steel
structures was initiated to compile in 1998 and formally
issued in 2000 for steel construction in Shanghai. The
analytical approach is adopted in this code, which is
validated through experiments and extended to the CECS
(China Association for Engineering Construction Standar-
dization) code in 2006 (Chinese standard, 2006). Mainly
based on CECS code with adopting the recent achieve-
ments in assessing the insulation property of fire protec-
tion materials (Li et al., 2012), the national code has been
developed (Chinese National code, 2012). The key points
of the national code are presented in this paper.
2. Fire Duration Requirements of Structural Components
The aim of the code is to prevent the structure of a buil-
ding subject to fire from collapsing, ensure safe evacua-
tion of building occupants, and reduce the indirect econo-
mical loss due to the failure of the building and the cost
for repairing the damages of the structure caused by fire.
For this purpose, the requirements on the fire duration of
†Corresponding author: Guo-Qiang LiTel: +86-21-6598-2975; Fax: +86-21-6598-3431E-mail: gqli@tongji.edu.cn
124 Guo-Qiang Li et al. | International Journal of High-Rise Buildings
structural components in various buildings are stipulated
in this code, as shown in Table 1.
The fire-resistance duration requirement of a structural
component is related to the function of the component in
the structure and the grade of the building that the struc-
ture serves for. The more important is the structural com-
ponent, the more serious the fire-resistance.
3. Steel Properties at Elevated Temperatures
Because there is no distinct yield strength for steel at
elevated temperatures, various effective yield strength of
steel at elevated temperatures have been recommended in
various codes. Based on the results achieved in Tongji
university, the stress under condition of the strain, 1.5%,
is adopted as the effective yield strength of steel at
elevated temperatures in the Chinese code, which can be
expressed with
(1)
where
(2)
here, Ts is the steel temperature; fyT is the effective yield
strength of steel at elevated temperature; fy is the yield st-
rength of steel at ambient temperature; and ηT is the reduc-
tion factor of the yield strength of steel at elevated tem-
perature.
The elastic modulus of steel at elevated temperatures
can be determined by
(3)
(4)
here, ET and E are the elastic modulus of steel at eleva-
ted and ambient temperature, respectively; and χT is the
reduction factor of elastic modulus of steel at elevated
temperature.
The effective yield strength and elastic modulus at ele-
vated temperatures proposed in various codes are compa-
red in Figure 1(a) and (b), respectively. It can be seen that
the yield strength of steel at elevated temperatures used in
China code is close to that adopted in BS5950 with strain
of 1.5%.
4. Insulation Property of Fire Protection Materials
The insulation property of fire protection materials,
which is either intumescent or inorganic, can be assessed
by the concept equivalent thermal resistance, calculated by
(5)
where, Ri is the equivalent thermal resistance of the in-
sulation; Tcrit is the typical critical steel temperature, often
taken as 540oC; T0 is the initial steel temperature, taken as
20oC; tcrit is the fire duration time when the steel tempera-
fyT ηTfy=
ηT
1.0 20°C Ts 300°C≤ ≤
1.24 108–Ts
3× 2.096 105–Ts×– 300°C Ts 800°C< <
+9.228 103–Ts× 0.2168–
0.5 Ts/2000– 800°C Ts 1000°C≤ ≤⎩⎪⎪⎨⎪⎪⎧
=
ET χTE=
χT
7Ts 4780–
6Ts 4760–------------------------ 20°C Ts≤ 600°C<
1000 Ts–
6Ts 2800–------------------------ 600°C Ts 1000°C≤ ≤
⎩⎪⎪⎨⎪⎪⎧
=
Ri5 10
5–×Tcrit T
0–
tcrit------------------ 0.2+⎝ ⎠⎛ ⎞
2
0.044–
-------------------------------------------------------Ai
V----⋅=
Table 1. Fire-resistance duration requirements of structural components (h)
Feature of structural componentsGrade of buildings
Grade I Grade II Grade III Grade IV
Column and brace 3.00 2.50 2.00 0.50
Girder and truss 2.00 1.50 1.00 0.50
Floor slab 1.50 1.00 0.50 0.25
Roof component 1.50 0.50 - -
Exit stair component 1.50 1.00 1.00 -
Figure 1. Comparisons of the yield strength and elastic modulus reduction factor between various codes.
The Chinese Performance-based Code for Fire-resistance of Steel Structures 125
ture reaches the critical value Tcrit; and A i/V is the section
factor of the member, in which A i is interior face area of
the fire insulation per unit length and V is volume of the
component per unit length.
Intumeacent coatings are reactive fire proofing materials.
The behavior of intumescent coatings under heating is very
complex and no agreeable model is available to simulate
the behavior. The equivalent thermal resistance provide a
simple and valid way to assess the fire resistance of intu-
mescent coatings (Li et al., 2012).
5. Fundamental Requirements on the Fire Safety Design of Steel Components
For the fire safety of steel components, it is required
that
(6)
or
(7)
where td and tm are the actual and required fire-resistant
duration of structural components, respectively; Rd is the
actual load-bearing capacity of structural components in
required fire duration; and Sm is the combined loading
effect of structural components in required fire duration.
6. Fire Curves and Steel Temperature Calculations
6.1. Temperature increasing in normal compartment fire
The standard temperature-time curve recommended by
ISO834 is adopted for the gas temperature increasing in
normal compartment fire, which is expressed as:
(8)
where, Tg(t) is gas temperature at time t; Tg(0) is ambi-
ent gas temperature; and t is time in minutes.
6.2. Temperature increasing in hydrocarbon fire
The hydrocarbon temperature time curve is given by
(9)
6.3. Steel temperature calculation
Under the assumption of uniform temperature distribu-
tion in a steel component subjected to fire, the tempera-
ture increasing in the steel component in a interval ∆ t can
be determined with:
(10)
Where Ts(t) is the steel temperature at time t; ρs is the
density of steel; cs is the specific heat of steel; B is the
comprehensive heat transfer coefficient, for components
without fire insulation,
(11)
for components with fire insulation,
(12)
where: αc is the convective heat transfer coefficient bet-
ween gas and component, taken as 25 W/(m2·K) for stan-
dard fire; αr is the radiant heat transfer coefficient bet-
ween gas and component, which can be determined by
(13)
λi is thermal conductivity of fire protection material; di
is thickness of the insulation; ci is specific heat of the fire
protection material; A is surface area of the component
per unit length exposed to fire; Ai is interior face area of
the fire insulation per unit length; and V is volume of the
component per unit length.
When the ISO 834 fire atmosphere temperature increase
is employed for structural fire-resistant design, a simpli-
fied formula for predicting the temperature increasing in
the steel component is proposed in the code. It is expre-
ssed as
(14)
7. Capacity of Various Components in Fire
With temperature elevation caused by fire, the strength
and elastic modulus of steel components will be reduced.
The formulas recommended by ECCS (1983) governing
the reduction of elastic modulus and yield strength of steel
are employed in the code. With the reduced elastic modu-
lus and yield strength of steel under high temperature due
to fire, the load bearing capacity of various steel compo-
nents can be formulated with the same approach as for the
situation of normal temperature.
7.1. Axial tension component
The capacity of an axial tension steel component under
fire condition is governed by
(15)
where N is the combined axial force effect in the
component under fire condition; An is the net area of cross
section of the component; and γR is the safety factor for
fire condition.
7.2. Axial compression component
The capacity of an axial compression steel component
under fire condition is determined by
td tm≥
Rd Sm≥
Tg t( ) Tg 0( )– 345 8t 1+( )10
log=
Tg t( ) Tg 0( )– 1080 1 0.325et/6–
– 0.675e2.5t–
–( )×=
Ts t t∆+( ) Ts t( )–B
ρ s cs⋅----------- Tg t( ) Ts t( )–[ ] t∆⋅ ⋅=
B αc αr+( )AV---=
B1
1ρi ci diAi
2ρscsV-----------------+
-------------------------λ i
di----⋅=
αr εrσTg 273+( )4 Ts 273+( )4–
Tg Ts–-----------------------------------------------------=
Ts 0.044 5.0+ 105– λ i
di----Fi
V----× 0.2–⎝ ⎠
⎛ ⎞t 20+=
N
An
----- γR fyT≤
126 Guo-Qiang Li et al. | International Journal of High-Rise Buildings
(16)
and
(17)
where ϕ is factor of stability for the axially compressed
steel component at normal temperature; and α is coeffi-
cient, as listed in Table 3.
7.3. Bending component
The capacity of a bending steel component is governed
by
(18)
and
(19)
where Mx is the maximum moment in the component
under fire condition; Wx is the modulus of the component
cross-section; ϕ b is the factor of stability for the bending
component at normal temperature; ϕ bT is the factor of sta-
bility for the bending component at elevated temperatures;
and αb is a coefficient determined by
,
0oC < Ts ≤ 500oC (20)
,
500oC < Ts ≤ 600oC (21)
7.4. Compression and bending component
The capacity of compression and bending steel compo-
nents under fire condition can be governed by
(22)
and
(23)
with
(24)
(25)
where βm and β t are equivalent moment factors; N'ExT= 1.1(π2ETA/λx
2) and N'EyT = 1.1(π2ETA/λy2) are Euler cri-
tical load of the component in the bending plane at eleva-
ted temperatures, in which λx and λy are the slenderness
of the component and ET is the elastic modulus of steel at
elevated temperatures; γx is factor representing the plas-
ticity development, taken as 1.05 for I and box sectional
component; ϕ xT and ϕ yT are factors of stability for the
axially-compressed steel component in the bending plane
and out of the bending plane respectively at elevated
temperatures; and ϕ bxT and ϕ byT are the factors of stability
for the bending component about x and y axis at elevated
temperatures
7.5. Steel column in frameworks
In a frame subjected to fire, the columns may yield be-
cause of the thermal expansion of the adjacent beams, as
shown in Figure 2. The stability of the columns can be
checked by the following simple expression,
(26)
7.6. Steel girder in frameworks
The lateral buckling of steel girders in a frame are
usually prevented through bracing of floor slabs. Since
the girders in a frame is restrained by adjacent
components, the axial force in the girder subjected to fire
may vary from compression to tension with development
of the deflection of the girder, as shown in Figure 3. The
load bearing capacity of steel girder in frameworks
subjected to fire is checked at the state when the
compressive axial force in the girder is reduced to zero,
thus
(27)
where M is the maximum bending moment in the gir-
der; and Wp is the plastic section modulus of the girder.
N
ϕ TA--------- γR fyT≤
ϕ T αϕ=
Mx
ϕ bTWx
--------------- γR fyT≤
ϕ bT
αbϕ b αbϕ b 0.6≤
1.070.282
αbϕ b
-------------– 1.0≤ αbϕ b 0.6>⎩⎪⎨⎪⎧
=
αb 1.150 0.154sinTs
460---------π 0.46π–⎝ ⎠⎛ ⎞+=
αb 1.292 0.6565– 104–Ts 500–( )2×=
N
ϕxTA-----------
βmxMx
γxWx 1 0.8N/N ′ExT–( )------------------------------------------------ η
β tyMy
ϕ byTWy
-----------------+ + γR fyT≤
N
ϕyTA----------- η
β txMx
ϕ bxTWx
-----------------βmyMy
γyWy 1 0.8N/N′EyT–( )------------------------------------------------+ + ηsTγR f≤
N′ExT π2EsTA/ 1.1λx
2( )=
N′EyT π2EsTA/ 1.1λy
2( )=
N
ϕ TA--------- 0.7γR fyT≤
M γR fyTWp≤
Table 2. Coefficient α
Slenderness ratioof components
Temperature of structural components (oC)
200 300 400 500 550 570 580 600
≤ 50 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0.96
100 1.04 1.08 1.12 1.12 1.05 1.00 0.97 0.85
150 1.08 1.14 1.21 1.21 1.11 1.00 0.94 0.74
≥ 200 1.10 1.17 1.25 1.25 1.13 1.00 0.93 0.68
Figure 2. Columns in a frame yielding in fire condition.
The Chinese Performance-based Code for Fire-resistance of Steel Structures 127
7.7. Concrete slab with metal decking
If the deflection of the slab with metal decking is requi-
red to be limited to a small value in fire, the fire-resistant
duration of the slab can be determined by
(28)
where FR is the fire-resistant duration of the slab with
metal decking, in minutes; Mmax is the maximum bending
moment by applied load in unit width of slab; ft is the ten-
sile design strength of concrete at ambient temperature;
W is the section modulus in unit width of the part of con-
crete where temperature is below 700oC. The temperature
contour of 700oC at different time in the slab is shown in
Figure 4.
If large deflection of slab is allowable, a simplified ap-
proach for estimating the fire-resistance of the slab consi-
dering membrane action is recommended in the code, ac-
cording to the research achievement by Bailey et al. (2000)
and H. S. Zhou (2004).
7.8. Steel-concrete composite beam
The load bearing capacity of composite beams at eleva-
ted temperatures can be checked by
for simply supported beam (29)
for rotationally restrained beam (30)
where M is the maximum bending moment in the beam
produced by applied load under the condition of simple
support, M = ql2/8 for uniformly distributed load; is
the sagging bending capacity of the beam at elevated tem-
peratures; is the hogging bending capacity of the beam
at elevated temperatures.
If the neutral axis is in the concrete, as shown in Figure
5, can be determined by
(31)
where C1 is the compressive force in the concrete; F1 is
the tensile force of the top flange of steel beam after it is
yield; F2 is the tensile force of the web and the bottom
flange of steel beam after it is yield; hC1 is the distance
between the position of C1 and the center of the bottom
flange of steel beam; hF1 is the distance between the po-
sition of F1 and the center of the bottom flange of steel
beam; hF2 is the distance between the position of F2 and
the center of the bottom flange of steel beam.
If the neutral axis is in the steel beam, as shown in Figure
6, can be determined by
(32)
where is the compressive force when the total
area of the concrete is compressed to yielding; =
0.5(−C1 − F1 − F2 + F3) is the compressive force of the
part of the web in compression; = 0.5(C1 + F1 + F2 −
F3) is the tensile force of the part of the web in tension;
F3 is the tensile force of the bottom flange of steel beam
after it is yield; is the distance between the position
of and the center of the bottom flange of steel beam;
is the distance between the position of and the
center of the bottom flange of steel beam.
Based on the stress distribution for a composite beam in
hogging bending region as shown in Figure 7, may be
given by
(33)
where = 0.5(F1 + F2) is the compressive force of
the part of the web in compression; = 0.5(−F1 + F2)
is the tensile force of the part of the web in tension;
is the distance between the position of and the cen-
ter of the top flange of steel beam; is the distance bet-
ween the position of and the center of the top flange
of steel beam; e3 is the distance between the position of
FR 114.06 26.8Mmax
ftW------------–=
M MR
+≤
M MR
+MR
−
+≤
MR
+
MR
−
MR
+
MR
+hC1C1
hF1F1– hF2F2
–=
MR
+
MR
+hC1C1
totalhF1F1
hF2com
F2
comhF2tenF2
ten–+ +=
C1
total
F2
com
F2
ten
hF2com
F2
com
hF2ten
F2
ten
MR
−
MR
−
hy2com
Fy2
comhy2tenFy2
ten–=
Fy2
com
Fy2
ten
hy2com
Fy2
com
hy2ten
Fy2
ten
Figure 3. The development of axial force in a restrainedgirder in fire condition.
Figure 4. The temperature contour of 700oC in the slab.Figure 5. The profile of a composite beam and the stressdistribution when the neutral axis is in the concrete.
128 Guo-Qiang Li et al. | International Journal of High-Rise Buildings
the neutral axis and the center of the top flange of steel
beam.
8. Experimental Validation
In order to validate the effectiveness of the approach for
the fire safety design of steel components presented herein-
above, a series of experiments have been carried out in
Tongji University (Li & Jiang, et al., 2000) on steel colu-
mns, steel beams and steel-concrete composite beams sub-
ject to fire.
8.1. Experiments on the axially compressed and eccen-
trically compressed steel columns
The purpose of the experiments is to validate the fire
safety design method employed by the Code for axially
and eccentrically compressed steel columns. The axially
compressed specimen is a box column welded by steel
plate with a thickness of 20 mm, and the eccentrically
compressed specimen is also a box column welded by
steel plate with a thickness of 30 mm, as shown in Figure
8. The height of the columns is 3810 mm, but only a seg-
ment of 3000 mm of the columns were enclosed in the
stove. The slenderness ratio of the axially compressed one
is 22.2 and that of the eccentric column is 25.2. The off-
setting of the load for the eccentrically compressed column
is 120 mm. The column specimens were made of Q235
steel, the yielding strength and Young’s modulus of which
are 255 MPa and 1.85×105 MPa, respectively. The speci-
mens were protected by fireproof paint with a thickness
of 10 mm, and the thermal conductivity of 0.12 W/(m·K).
Figure 8 Sketches of specimens of columnsshows some
pictures of the tested column.
The load on the specimens was kept constant while the
temperature in the stove increased according to ISO834
standard. The load for axially compressed column speci-
men was 4116 kN and that for eccentrically compressed
column specimen was 3528 kN. Figure 10 shows the vari-
ation of the axial deformation of the specimens with the
lasting time of fire exposures. The fire-resistant duration
of the axially compressed column and the eccentrically
compressed column were measured 88 minutes and 85.2
minutes, respectively.
8.2. Experiments on the axially restrained steel beam
The purpose of the experiments is to validate the fire
safety design method employed by the code for bending
beams with thermal effects due to restraints. A beam spe-
cimen welded by three plates is shown in Figure 11. The
steel for the specimen is Q235, the yielding strength of
which is 225 MPa and the Young’s modulus is 1.85 MPa.
The specimen was protected by fireproof paint with a thi-
ckness of 15 mm and the thermal conductivity of 0.102
W/(m·K).
Figure 6. The profile of a composite beam and the stressdistribution when the neutral axis is in the steel beam.
Figure 7. The stress distribution for a composite beam inhogging bending region.
Figure 8. Sketches of specimens of columns.
Figure 9. Specimens of columns in the stove.
Figure 10. The variation of axial deformation with time.
The Chinese Performance-based Code for Fire-resistance of Steel Structures 129
Figure 12 shows the furnace for the fire-resistant experi-
ment on the beam. The ends of the beam were restrained
by a truss. The truss is heavily insulated by ceramic ma-
terials with a thickness of 40 mm. So the axial expansion
of the beam is restrained when heated and the thermal
effects on the beam was simulated. Four point loads were
applied on the beam, as shown in Figure 13.
The ISO834 standard fire was also adopted for the beam
specimen. The axial force in the beam due to the restraint
of the truss was measured to be 1140 kN when the beam
failed. The measured fire-resistance duration of the beam
was 54 minutes.
8.3. Experiments on simply supported composite beams
In order to investigate the behaviour of composite beams
subjected to fire, experiments on two specimens of steel-
concrete composite beams were conducted. The spans of
the both specimens are 5.1 m. The distribution of applied
load is shown in Figure 14. The yield strengths of the steel
beam is 250 MPa. The compressive strength of the conc-
rete is 33.3 MPa. The beam is protected by fireproof paint
with 10 mm in thickness.
The profiles of the two specimens are shown in Figure
15. For specimen I, the cross-sectional size of the steel
beam is H400X150X8X12, and the width of the concrete
slab is 1376 mm. Each point load applied on specimen I
is 100 kN. For specimen II, the cross-sectional size of the
steel beam is H300X150X8X8, and the width of the con-
crete slab is 1350 mm. Each point load applied on speci-
men II is 75 kN. The developments of deflections of the
two specimens are shown in Figure 16. It is found that
composite beams are damaged in fire with a transversal
crack at mid-span. The measured fire-resistant durations
Figure 11. Configuration of the beam.
Figure 12. The configuration of furnace for the experimenton beam.
Figure 13. Loads on the beam specimen.
Figure 14. Testing assembly.
Figure 15. The profile of the specimens.
Figure 16. The development of deflections of compositebeam specimens.
130 Guo-Qiang Li et al. | International Journal of High-Rise Buildings
of the two specimens of composite beams were 55 and
45 min, respectively.
8.4. Comparison between prediction and measurement
The fire-resistance duration of the axially compressed
column, the eccentrically compressed column and the res-
trained beams can be predicted through the approach pro-
posed in the Chinese code. The comparison between the
results obtained by the experimental measurement and the
Code prediction is shown in Table 3. It can be seen that
the fire-resistance of steel components can be satisfac-
torily predicted with the Code.
To validate the approach for evaluating the capacity of
steel-concrete composite beams in fire presented in the
code, the limit capacity for the point load applied on the
two composite beam specimens described hereinabove are
predicted with the approach in the code and compared with
the experimental results, as shown in Table 4.
9. Concluding Remarks
The main content of Chinese national code on Fire Safety
Design of Steel Structures is presented in this paper. The
principle of the code is to meet the requirements of fire-
resistance on the basis of limit state of steel structures under
fire condition. The analytical approach is employed in the
code for the fire safety of various steel components through
checking the load-bearing capacity of the components ex-
posed to a fire in the time of required fire resistant dura-
tion. The effects of the load level, thermal action and struc-
tural restraints on the fire-resistance of steel components
can be considered. The effectiveness of the approach adop-
ted by the Code is validated through experiments.
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Table 3. The comparison between measurement and prediction for fire-resistance duration of specimens
Members Predicted (min) Measured (min) Relative error
Axiallycompressed column 94 88 6.82%
Eccentrically compressed column 90 85.2 5.63%
Axiallyrestrained beam 53.8 54 0.4%
Table 4. The comparison between measurement and pre-diction for the capacity supporting the point load on com-posite beam specimens
MembersPredicted
(kN)Measured
(kN)Relative
error
Specimen I 103 100 3%
Specimen II 78 75 4%
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